Previously, the development of communication systems included all parts of the respective system such as a core network part, an access network part etc. This has for example been the case for second generation (mobile) communication systems such as GSM (Global System for Mobile Communications).
However, in recent years, the development of new communication systems as well as the further development of existing communication systems tends to be of rather heterogeneous nature. That is, the development of the single parts of a communication system has drifted apart from each other, thus nowadays being independent of each other. Furthermore, there have been developed many co-existing technologies underlying the single parts and the whole of a communication system. This has for example been the case for third generation (mobile) communication systems such as UMTS (Universal Mobile Telecommunications System).
Consequently, there have recently emerged communication systems, for example mobile communication systems, having a heterogeneous multi-access environment. Stated in other words, such systems comprise multiple access networks each operating according to an individual access technology, such as WCDMA, cdma2000, GPRS etc. (CDMA: code division multiple access).
Generally, in communication systems enabling mobility, i.e. mobile communication systems, there is a necessity that a roaming user or node gets access to a visited communication network (i.e. a communication network other than its home network). In a communication system with multiple access networks or technologies, the access can be provided by any one of the access networks or technologies as long as the roaming user or node is able to operate according to this network or technology.
However, in such a scenario there exists a problem when a roaming user or node arrives at a new visited network for the first time. If so, it may take a relatively long time before the visited network is able to grant access to the user or node, because it needs to contact the user's home network or subscription provider before being bale to decide whether the user is entitled to get an access or not. Furthermore, there exists a problem when a user or node already having access at one access network hands over to another access network or technology within the same visited network (i.e. of the same visited network operator). Another problem may even exist when the user or node hands over from one access network to another access network within the same access technology and visited network operator. In all of these cases, the required handover procedure and the associated signaling according to conventional approaches take some time which then affects the user experience in terms of connectivity and service break.
Hitherto, there has been proposed no solution to these problems linked with multi-access environments. Rather, previously known solutions, such as those defined by the Third Generation Partnership Project 3GPP, only address a similar problem and focus on a 3G (third generation according to the) mobile cellular network environment, i.e. aiming to decrease the signaling delay. Examples for such conventional approaches may include the so-called Turbo Charger approach as e.g. defined in the document “3GPP-TR 23.913 V1.0.0 (1999-12)” and the so-called Gateway Location Register approach as e.g. defined in the document “3GPP-TS 23.119 V6.0.0 (2004-12)”.
These approaches more particularly relate to subscription handling related signaling optimization between network boundaries, and have several drawbacks. The Turbo Charger approach for example, among others, is only applicable for UMTS networks, limits the number of subscribers registered in a network, and introduces additional complexity to the network architecture in terms of additional network elements required and their operation.
Also, since the approaches mentioned above are aimed for 3G cellular networks having a homogenous access environment, they are not applicable in generic heterogeneous multi-access environments and thus not sufficient to solve the problems described above in connection with such multi-access environments.
Thus, a solution to the above problems and drawbacks is needed particularly for multi-access network environments.